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This work is based upon a simulation model for spark-ignition engines that considers the instantaneous heat transfer, the combustion process occurring at a finite rate as well as intake and exhaust processes. The model calculates the thermodynamic properties - including exergy - of each gas mixture composition of the working fluid. Besides the common features of thermodynamic simulation models, the determination of instantaneous irreversibilities, exergetic efficiencies of each process and an overall cycle exergetic analysis are also included. Based upon the simulation model, first and second law analysis are applied to a parametric study with emphasis in the combustion process and the valve timing effects. Exergy destructions taking place during the combustion of an ethanol fueled engine and a gasoline version of the same engine are compared.

The controlled emissions limits defined to passenger cars are becoming very stringent. Therefore, the first minutes of the emissions test cycles gained importance. This work deals with a strategy to reduce the emissions of NMHC, CO and NOx in the cold phase of the test cycle, while the engine and catalyst are cold. Leaving the engine, the exhaust gases pass through a three- way catalyst to reduce controlled pollutant gases, but the catalyst is effective only above 300°C (the so-called light-off temperature). When the catalyst is not hot enough, the gases pass through the catalyst without any beneficial effect. In modern engines, most of the NMHC emissions occur in the cold phase; then, reducing this pollutant in the cold phase is the main objective of the adopted strategy. Besides, significant amounts of CO and NOx are formed during this phase and this must also be considered.